Method for estimating distance, and system and computer-readable medium for implementing the method

ABSTRACT

A method for estimating a distance between a first target and a second target in an image is to be implemented using a distance estimation system that includes a processor module. In the method, the processor module is programmed to: generate an image depth map associated with the image; generate first position information associated with a first position which corresponds to the first target in the image, and second position information associated with a second position which corresponds to the second target in the image; and compute an estimate of a distance between the first target and the second target based on at least the image depth map, the first position information, and the second position information.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continued Application of U.S. patent applicationSer. No. 14/852,963, filed 14 Sep. 2015, currently pending, and whichclaims priority of Chinese Patent Application No. 201410813662.0, filedon Dec. 24, 2014.

FIELD

The disclosure relates to a method, a system and a computer-readablemedium for estimating distance, more particularly to a method, a systemand a computer-readable medium for estimating a distance between a firsttarget and a second target in an image based on an image depth map ofthe image.

BACKGROUND

As fabrication processes of semiconductors improve, mobile devices suchas mobile phones and tablets are incorporated with more functionalities(e.g., having a camera for capturing an image and/or a video), aremanufactured with lower cost, and are therefore becoming widely used.However, conventional mobile devices are unable to directly obtain asize of an object (or a distance between two targets) in the imagecaptured thereby. Currently, one way of obtaining the size of the objectis to place a reference object (e.g., a coin, a ruler, etc .) near theobject in order to obtain an estimate of the size, which is inconvenientand inaccurate.

SUMMARY

Therefore, an object of the disclosure is to provide a method that canprovide a more convenient way of obtaining an estimate of a size of anobject and/or a distance between two targets in an image.

According to the disclosure, the method for estimating a distancebetween a first target and a second target in an image is to beimplemented using a distance estimation system. The distance estimationsystem includes a processor module. The method includes the steps of:

generating, by the processor module, an image depth map associated withthe image;

generating, by the processor module, first position informationassociated with a first position which corresponds to the first targetin the image, and second position information associated with a secondposition, which corresponds to the second target in the image; and

computing, by the processor module, an estimate of a distance betweenthe first target and the second target based on at least the image depthmap, the first position information and the second position information.

Another object of the disclosure is to provide a distance estimationsystem that is programmed to implement the aforementioned method.

According to the disclosure, the distance estimation system is forestimating a distance between a first target and a second target in animage. The distance estimation system includes a processor module thatis programmed to:

generate an image depth map associated with the image;

generate first position information associated with a first positionwhich corresponds to the first target, and second position informationassociated with a second position which corresponds to the secondtarget; and

compute an estimate of a distance between the first target and thesecond target based on at least the image depth map, the first positioninformation and the second position information.

Yet another object of the disclosure is to provide a non-transitorycomputer-readable medium. According to the disclosure, thenon-transitory computer-readable medium stores a software applicationtherein. The software application includes instructions that, whenexecuted by a processor module of a distance estimation system, causesthe processor module to perform a method for estimating a distancebetween a first target and a second target in an image. The methodincludes the steps of:

generating an image depth map associated with the image;

generating first position information associated with a first positionwhich corresponds to the first target, and second position informationassociated with a second position which corresponds to the secondtarget; and

computing an estimate of a distance between the first target and thesecond target based on at least the image depth map, the first positioninformation and the second position information.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the disclosure will become apparent inthe following detailed description of the embodiments with reference tothe accompanying drawings, of which:

FIG. 1 is a block diagram of a distance estimation system for estimatinga distance, according to a first embodiment of the disclosure;

FIG. 2 is a flow chart depicting steps of the method for estimating adistance that is to be implemented by the distance estimation system asdepicted in FIG. 1;

FIG. 3 illustrates an image displayed by a display module of thedistance estimation system;

FIG. 4 illustrates operations of computing an estimate of a distancebetween a first target and a second target in the image according to thefirst embodiment;

FIG. 5 is a block diagram of a distance estimation system for estimatinga distance, according to a second embodiment of the disclosure;

FIG. 6 illustrates operations of computing an estimate of a distancebetween a first target and a second target in the image according to thesecond embodiment;

FIG. 7 illustrates operations of computing an estimate of a distancebetween a first target and a second target according to a thirdembodiment;

FIG. 8 is a flow chart depicting steps of the method for estimating adistance that is to be implemented by the distance estimation system asdepicted in FIG. 5, according to the second embodiment; and

FIG. 9 is a flow chart depicting steps of the method for estimating adistance that is to be implemented by the distance estimation system asdepicted in FIG. 1, according to the third embodiment.

DETAILED DESCRIPTION

Before the disclosure is described in greater detail, it should be notedthat like elements are denoted by the same reference numerals throughoutthe disclosure.

FIG. 1 is a block diagram of a distance estimation system for estimatinga distance, according to the first embodiment of the disclosure. Thedistance estimation system includes an image capturing module 11, aninput module 12, a display module 13, a sensor module 14, a processormodule 15, and a computer-readable medium 16.

The image capturing module 11 has stereopsis functionality. That is, animage captured by the image capturing module 11 includes informationregarding a depth of each object captured in the image. As a result, theimage captured by the image capturing module 11 may allow a person toidentify relative depths of objects contained in the image. The imagecapturing module 11 may include a lens and an image sensor, and iscapable of image capturing.

It is noted that, in various embodiments, one or more additional lensesand image sensors may be included in the image capturing module 11. Forexample, in one embodiment, a plurality of image sensors are included,and each time when the image capturing module 11 is used for imagecapturing, a plurality of images are obtained, each corresponding with arespective one of the image sensors. In another embodiment, a pluralityof lenses are included, and each time when the image capturing module 11is used for image capturing, a plurality of images are obtained, eachcorresponding with a respective one of the lenses.

The input module 12 may be embodied in a touchscreen, a set of buttons,or a combination thereof, to serve as a user interface for receivinguser input. The display module 13 is configured to display the image.The sensor module 14 is configured to detect a tilt angle of the imagesensor with respect to an imaginary vertical line. For example, theimaginary vertical line is perpendicular to a horizontal plane such as aground. The processor module 15 is coupled to the image capturing module11, the input module 12, the display module 13, the sensor module 14,and the computer-readable medium 16.

The computer-readable medium 16 stores a software application therein.The software application includes instructions that, when executed bythe processor module 15, causes the processor module 15 to perform amethod for estimating a distance. In practice, the software applicationmay be stored in the computer-readable medium 16 or downloaded via anetwork.

In this embodiment, the distance estimation system may be embodied in amobile device such as a smart phone, a digital camera, a tabletcomputer, etc.. Accordingly, the image capturing module 11 is a cameramodule, the input module 12 is a touchscreen interface, the displaymodule 13 is a display screen, the sensor module 14 is a gyroscope orother components capable of detecting a tilt angle of the mobile device(i.e., with respect to a pitch axis, a roll axis or a yaw axis), and thecomputer-readable medium 16 is a storage medium of the mobile device.

It is noted that in other embodiments, the tilt angle of the mobiledevice may be calculated using, for example, trigonometric functions,and the sensor module 14 may be omitted.

In other embodiments, the distance estimation system may be embodied ina combination of a computer and a device capable of capturing an image,such as a mobile device, an event data recorder (EDR), a monitoringdevice, a rear view camera, etc . . . In this case, the input module 12is a mouse and/or keyboard of the computer, the display module 13 is ascreen of the computer, the sensor module 14 is a gyroscope or othercomponents capable of detecting a tilt angle of the device capable ofcapturing an image, the processor module 15 is a processor of thecomputer such as a CPU, and the computer-readable medium 16 is a storagemedium of the computer such as a random access memory (RAM), anelectrically-erasable programmable read-only memory (EEPROM), a compactdisc read-only memory (CD-ROM), a hard disk, etc . . .

It is noted that in other embodiments, the tilt angle of the devicecapable of capturing an image may be calculated using, for example,trigonometric functions, and the sensor module 14 may be omitted.

FIG. 2 is a flow chart depicting, according to the first embodiment ofthe disclosure, steps of the method for estimating a distance that is tobe implemented by the distance estimation system as depicted in FIG. 1.

The method as illustrated in FIG. 2 is used to compute an estimate of anactual distance between a first target and a second target in an imagecaptured by the image capturing module 11. For example, the input module12 and the display module 13 are integrated as a touchscreen, and thefirst and second targets are selected by a user using the touchscreen.This may be done by the user touching two positions (i.e. first andsecond positions being selected) on the image displayed by the displaymodule 13, and the first and second positions on the image serve as thefirst and second targets (as shown in FIG. 3), respectively.

In step S1, for the image captured by the image capturing module 11, theprocessor module 15 generates an image depth map associated with theimage. The image depth map contains information regarding a distancebetween a surface of each of the targets captured in the image and aviewpoint, which generally indicates the position of the lens.

It is noted that in other embodiments, operations for generating theimage depth map may employ one or more images captured by the imagecapturing module 11 for improved accuracy.

In step S2 the processor module 15 generates first position informationassociated with a first position which corresponds to the first target,and second position information associated with a second position whichcorresponds to the second target. In particular, the first positioninformation includes a set of coordinates of the first position on theimage where the first target is located. Similarly, the second positioninformation includes a set of coordinates of the second position on theimage where the second target is located.

In step S3, the processor module 15 controls the display module 13 todisplay a first mark at the first position, and to display a second markat the second position. Referring to FIG. 3, the display module 13displays the image having a cabinet (O). When the user touches twocorners of the cabinet (O) (the two corners serve as the first andsecond targets, respectively), the display module 13 is controlled todisplay two marks (D₁ and D₂) indicating the first and second positionsselected by the user.

In step S4,the processor module 15 computes the estimate of the distancebetween the first target and the second target based on at least theimage depth map, the first position information, and the second positioninformation. Specifically, step S4 includes the following sub-steps S41and S42.

In sub-step S41, the processor module 15 estimates a first targetdistance between the first target and the lens based on the firstposition information, the image depth map, a focus length of the lensfor capturing the image, and a pixel size of the image sensor.

In sub-step S42, the processor module 15 computes the estimate of thedistance between the first target and the second target, based on atleast the first target distance, the first position information, thesecond position information, and the focus length of the lens. Thesub-step S42 further includes the following sub-steps S421 to S423.

In sub-step S421, the processor module 15 obtains a first pixel positionand a second pixel position on the image sensor, based respectively onthe first position information and the second position information. Thefirst and second pixel positions correspond to the first and secondpositions in the image, respectively. In sub-step S422, the processormodule 15 calculates a distance between the first pixel position and thesecond pixel position on the image sensor. In sub-step S423, theprocessor module 15 computes the estimate of the distance between thefirst target and the second target based on the first target distance,the distance between the first pixel position and the second pixelposition on the image sensor, the focus length of the lens, and the tiltangle of the mobile device.

FIG. 4 is a schematic view illustrating the image of the cabinet (O) ,as shown in FIG. 3, being captured by the image capturing module 11using perspective projection and the operations of computing an estimateof the distance. The lens has a focal point (M) and a focal length (f).The cabinet (O) has a height (h₁), which, in this case, is the actualdistance between the first target (T₁) and the second target (T₂). Theimage sensor (I) is tilted by a tilt angle (A) with respect to animaginary vertical line (L). The first and second targets (T₁, T₂)(i.e., the lower and upper corners of the cabinet (O)) are projectedrespectively on first and second pixel positions (Y₁) and (Y₂) on theimage sensor (I).

It is known that the triangle (ΔMT₁T₂) and the triangle (ΔMXY₂) aresimilar triangles (as seen in FIG. 4, the point (X) is located on theline T₁Y₁, and the triangle (ΔMXY₂) is a right triangle). Subsequently,the following relation holds:

$\begin{matrix}{\frac{L_{1} + L_{2}}{d\; 1} = \frac{L_{3}}{h\; 1}} & (1)\end{matrix}$

In sub-step S41, the first target distance (d₁) is obtained. Next, insub-step S421, the first and second pixel positions (Y₁, Y₂) areobtained. Therefore, a distance (h11) between the first and second pixelpositions (Y₁, Y₂) on the image sensor (I) can be calculated in sub-stepS422.

Subsequently, in sub-step S423, the estimate of the height (h₁) of thecabinet (O) (i.e., the actual distance between the first and secondtargets (T₁, T₂)) can be computed using the following equation:

$\frac{{h\; {11 \cdot {\sin (A)}}} + {f \cdot {\sec (A)}}}{d\; 1} = \frac{h\; {11 \cdot {\cos (A)}}}{h\; 1}$

since L₁=h11*sin(A), L₂=f*sec(A), and L₃=h11*cos(A). By taking the tiltangle into consideration, the estimation of the actual distance betweenthe first and second targets (T1, T2) may have improved accuracy.

In step S5, the processor module 15 controls the display module 13 todisplay the estimate of the height (h₁) (i.e., the actual distancebetween the first and second targets (T₁, T₂)). For example, the symbol“D:1M” in FIG. 3 indicates the height (h₁) of the cabinet (O) in theimage that is estimated to be one meter. It is noted that in otherembodiments, the first target and the second target may be parts ofdifferent objects captured in the image.

FIG. 5 illustrates a block diagram of a distance estimation system forestimating a distance, according to the second embodiment of thedisclosure. The difference between the distance estimation system inthis embodiment and that in the first embodiment resides in that thedistance estimation system of this embodiment omits the sensor module14.

The difference between the method in this embodiment shown in FIG. 8 andthat in the first embodiment resides in the computation of the estimateof the distance between the first target and the second target (i.e.,step S4). While the estimation in the first embodiment is more accurate,the estimation in this embodiment may be done with higher efficiency.

In sub-step S41′, the processor module 15 estimates the first targetdistance between the first target and the lens, and further estimates asecond target distance between the second target and the lens. Theestimations are based on the first position information, the secondposition information, the image depth map, the focus length of the lensfor capturing the image, and the pixel size of the image sensor.

In sub-step S42′, the processor module 15 computes the estimate of thedistance between the first target and the second target. The computingis based on at least the first target distance, the second targetdistance, the first position information, the second positioninformation, and the focus length of the lens.

FIG. 6 is a schematic view illustrating an object (O′) being captured bythe image capturing module 11 and the operations of computing theestimate of the distance. The lens has a focal point (M) and a focallength (f). The object (O′) has a height (h₂), which, in this case, isthe distance between the first target (T₁) and the second target (T₂).

In sub-step S41′, the processor module 15 estimates the first targetdistance (d₁) and the second target distance (d₂).

Next, in sub-step S421′, the processor module 15 obtains the first andsecond pixel positions (Y₁, Y₂). Therefore, a distance (h₃₃) between thefirst and second pixel positions (Y₁, Y₂) on the image sensor (I) can becalculated in sub-step S422′.

Afterward, in sub-step S423′, an estimate of the height (h₂) of theobject (O′) can be computed using the following equations:

h₂ = d₁² + d₂² − 2 ⋅ d₁ ⋅ d₂ ⋅ cos (K) $K = \frac{h_{33}}{f}$

It is noted that the angle (K) maybe obtained using small-angleapproximation. That is, the angle (K) can be approximated by the ratio(h₃₃/f). It is noted that the estimation is more accurate when the angle(K) is smaller. Moreover, the estimate of the height (h₂) is computedusing the law of cosines. Therefore, the estimation is more accuratewhen the tilt angle of the image sensor (I) is smaller, preferablysmaller than 20 degrees.

In a third embodiment, the distance estimation system as shown in FIG. 1is further provided with the function to assist the user to calibratethe image capturing module 11 such that the tilt angle of the imagesensor with respect to the imaginary vertical line is zero when theimage is captured. For example, the processor module 15 may control thedisplay module 13 to display a horizontal reference line, in order tovisually notify the user. In another example, the distance estimationsystem may output a visual signal (e.g., a light signal) when the tiltangle of the image sensor (I) with respect to the imaginary verticalline is zero.

The difference between the method in this embodiment shown in FIG. 9 andthat in the first embodiments resides in the computation of the estimateof the distance between the first target and the second target (i.e.,step S4).

FIG. 7 is a schematic view illustrating an object (O′) being captured bythe image capturing module 11 and the operations of computing theestimate of the distance. The lens has a focal point (M) whichcorresponds to a center point of the image sensor (I), and a focallength (f). The object (O′) has a height (h₂) , which, in this case, isthe distance between the first target (Y₁) and the second target (Y₂).The tilt angle of the image sensor (I) with respect to the imaginaryvertical line (L) is zero.

In sub-step S41″, the processor module 15 estimates the first targetdistance (d₁) and the second target distance (d₂).

Next, in sub-step S421″, the processor module 15 obtains the pixelpositions (Y₁, Y₂). In sub-step S422″, the processor module 15calculates a first distance (h₂₁) between the first pixel position (Y₁)and the center point of the image sensor (I), and a second distance(h₂₂) between the second pixel position (Y₂)and the center point of theimage sensor (I).

Afterward, in sub-step S423″, the estimate of the height (h₂) of theobject (O′) can be computed using the following equations:

h₂ = d₁ ⋅ sin (K₁) − d₂ ⋅ sin (K₂)$K_{1} = {\tan^{- 1}\frac{h_{21}}{f}}$$K_{2} = {\tan^{- 1}\frac{h_{22}}{f}}$

To sum up, the distance estimation system, method and computer-readablemedium according to the embodiments of the disclosure provides arelatively more convenient, reliable, and efficient way to obtain anestimate of a distance between two targets in the image, using the imagedepth map, the first position information, the second positioninformation, and parameters regarding the image capturing module 11(e.g., the focal length, size of pixels, etc.). The method as describedin the disclosure may be applied in calculating a size of one object (byselecting two extreme points of the one object as the targets) or incalculating a distance between two different objects. As a result, theimage captured by the distance estimation system as described in thedisclosure contains three-dimensional information.

While the disclosure has been described in connection with what areconsidered the exemplary embodiments, it is understood that thisdisclosure is not limited to the disclosed embodiments but is intendedto cover various arrangements included within the spirit and scope ofthe broadest interpretation so as to encompass all such modificationsand equivalent arrangements.

What is claimed is:
 1. A method for estimating a distance between afirst target and a second target in an image, the method to beimplemented using a distance estimation system that includes a processormodule, an image capturing module for capturing the image, the imagecapturing module including a lens and an image sensor, the methodcomprising: a) generating, by the processor module, an image depth mapassociated with the image; b) generating, by the processor module, firstposition information associated with a first position which correspondsto the first target in the image, and second position informationassociated with a second position which corresponds to the second targetin the image; and c) computing, by the processor module, an estimate ofa distance between the first target and the second target based on atleast the image depth map, the first position information and the secondposition information, wherein computing the estimate of a distancebetween the first target and the second target further includes: c-1)estimating, by the processor module, a first target distance between thefirst target and the lens based on the first position information, theimage depth map, a focus length of the lens for capturing the image, anda pixel size of the image sensor; and c-2) computing, by the processormodule, the estimate of the distance between the first target and thesecond target, based on at least the first target distance, the firstposition information, the second position information, and the focuslength of the lens.
 2. The method of claim 1, the distance estimationsystem further including a sensor module for detecting a tilt angle ofthe image sensor with respect to an imaginary vertical line, wherein,the step of computing the estimate of the distance between the firsttarget and the second target executed by the processor module includes:obtaining a first pixel position and a second pixel position on theimage sensor based respectively on the first position information andthe second position information, the first and second pixel positionscorresponding to the first and second positions in the image,respectively; calculating a distance between the first pixel positionand the second pixel position on the image sensor; and computing theestimate of the distance (h₁) between the first target and the secondtarget using the following equation:$\frac{{h_{11} \cdot {\sin (A)}} + {f \cdot {\sec (A)}}}{d_{1}} = \frac{h_{11} \cdot {\cos (A)}}{h_{1}}$where (h₁₁) represents the distance between the first and second pixelpositions on the image sensor, (A) represents the tilt angle, (f)represents the focus length of the lens, and (d₁) represents the firsttarget distance.
 3. The method of claim 1, wherein the step ofestimating a first target distance between the first target and the lensfurther estimates a second target distance between the second target andthe lens and additionally utilizes the second position information; andthe step of computing the estimate of the distance between the firsttarget and the second target additionally utilizes the second targetdistance.
 4. The method of claim 3, wherein, the step of computing theestimate of the distance between the first target and the second targetexecuted by the processor module includes: obtaining a first pixelposition and a second pixel position on the image sensor basedrespectively on the first position information and the second positioninformation, the first and second pixel positions corresponding to thefirst and second positions in the image, respectively; calculating adistance between the first pixel position and the second pixel positionon the image sensor; and computing the estimate of the distance (h2)between the first target and the second target using the followingequations: h₂ = d₁² + d₂² − 2 ⋅ d₁ ⋅ d₂ ⋅ cos (K)$K = \frac{h_{33}}{f}$ where (d₁) represents the first target distance,(d₂) represents the second target distance, (h₃₃) represents thedistance between the first and second pixel positions, and (f)represents the focus length of the lens.
 5. The method of claim 3 , thedistance estimation system further including a sensor module fordetecting a tilt angle of the image sensor with respect to an imaginaryvertical line, the image being captured when the tilt angle of thesensor module is equal to zero degree, wherein, the step of computingthe estimate of the distance between the first target and the secondtarget executed by the processor module includes: obtaining a firstpixel position and a second pixel position on the image sensor basedrespectively on the first position information and the second positioninformation, the first and second pixel positions corresponding to thefirst and second positions in the image, respectively; calculating afirst distance between the first pixel position and a center point ofthe image sensor, and a second distance between the second pixelposition and the center point of the image sensor; and computing theestimate of the distance (h₂) between the first target and the secondtarget using the following equations:h₂ = d₁ ⋅ sin (K₁) − d₂ ⋅ sin (K₂)$K_{1} = {\tan^{- 1}\frac{h_{21}}{f}}$$K_{2} = {\tan^{- 1}\frac{h_{22}}{f}}$ where (d₁) represents the firsttarget distance, (d₂) represents the second target distance, (h₂₁)represents the first distance, (h₂₂) represents the second distance, and(f) represents the focus length of the lens.
 6. The method of claim 1,the distance estimation system further including a display module,wherein the method further comprises the step of controlling, by theprocessor module, the display module to display the estimate of thedistance on the image.
 7. A distance estimation system for estimating adistance between a first target and a second target in an image, thesystem comprising a processor module that is programmed to: generate animage depth map associated with the image; generate first positioninformation associated with a first position which corresponds to thefirst target, and second position information associated with a secondposition which corresponds to the second target; and compute an estimateof a distance between the first target and the second target based on atleast the image depth map, the first position information and the secondposition information; the distance estimation system further comprisingan image capturing module that is configured for capturing the image andthat includes a lens and an image sensor, wherein the processor moduleis further programmed to: estimate a first target distance between thefirst target and the lens based on the first position information, theimage depth map, a focus length of the lens for capturing the image, anda pixel size of the image sensor; and compute the estimate of thedistance between the first target and the second target, based on atleast the first target distance, the first position information, thesecond position information, and the focus length of the lens.
 8. Thedistance estimation system of claim 7, further comprising a sensormodule for detecting a tilt angle of the image sensor with respect to animaginary vertical line, wherein the processor module is furtherprogrammed to: obtain a first pixel position and a second pixel positionon the image sensor based respectively on the first position informationand the second position information, the first and second pixelpositions corresponding to the first and second positions in the image,respectively; calculate a distance between the first pixel position andthe second pixel position on the image sensor; and compute the estimateof the distance (h₁) between the first target and the second targetusing the following equation:$\frac{{h_{11} \cdot {\sin (A)}} + {f \cdot {\sec (A)}}}{d_{1}} = \frac{h_{11} \cdot {\cos (A)}}{h_{1}}$where (h₁₁) represents the distance between the first and second pixelpositions on the image sensor, (A) represents the tilt angle, (f)represents the focus length of the lens, and (d₁) represents the firsttarget distance.
 9. The distance estimation system of claim 7, whereinthe processor module further estimates a second target distance betweenthe second target and the lens and additionally utilizes the secondposition information, and the processor module additionally computes theestimate of the distance between the first target and the second targetadditionally utilizing the second target distance.
 10. The distanceestimation system of claim 9, wherein the processor module is furtherprogrammed to: obtain a first pixel position and a second pixel positionon the image sensor based respectively on the first position informationand the second position information, the first and second pixelpositions corresponding to the first and second positions in the image,respectively; calculate a distance between the first pixel position andthe second pixel position on the image sensor; and compute the estimateof the distance (h₂) between the first target and the second targetusing the following equations: h₂ = d₁² + d₂² − 2 ⋅ d₁ ⋅ d₂ ⋅ cos (K)$K = \frac{h_{33}}{f}$ where (d₁) represents the first target distance,(d₂) represents the second target distance, (h₃₃) represents thedistance between the first and second pixel positions, and (f)represents the focus length of the lens.
 11. The distance estimationsystem of claim 9, further comprising a sensor module for detecting atilt angle of the image sensor with respect to an imaginary verticalline, the image being captured by the image capturing module when thetilt angle of the image sensor is equal to zero degree, wherein saidprocessor module is further programmed to: obtain a first pixel positionand a second pixel position on the image sensor based respectively onthe first position information and the second position information, thefirst and second pixel positions corresponding to the first and secondpositions in the image, respectively; calculate a first distance betweenthe first pixel position and a center point of the image sensor, and asecond distance between the second pixel position and the center pointof the image sensor; and compute the estimate of the distance (h₂)between the first target and the second target using the followingequations: h₂ = d₁ ⋅ sin (K₁) − d₂ ⋅ sin (K₂)$K_{1} = {\tan^{- 1}\frac{h_{21}}{f}}$$K_{2} = {\tan^{- 1}\frac{h_{22}}{f}}$ where (d₁) represents the firsttarget distance, (d₂) represents the second target distance, (h₂₁)represents the first distance, (h₂₂) represents the second distance, and(f) represents the focus length of the lens.
 12. The distance estimationsystem of claim 7, further comprising: a display module for displayingthe image thereon; and an input module that receives user-input of thefirst target and the second target in the image; wherein the processormodule is further programmed to control said display module to displaythe estimate of the distance on the image.
 13. A non-transitorycomputer-readable medium that stores a software application therein, thesoftware application including instructions that, when executed by aprocessor module of a distance estimation system, causes the processormodule to perform a method for estimating a distance between a firsttarget and a second target in an image, the distance estimation systemfurther including an image capturing module for capturing the image, theimage capturing module including a lens and an image sensor, the methodincluding: a) generating an image depth map associated with the image;b) generating first position information associated with a firstposition which corresponds to the first target, and second positioninformation associated with a second position which corresponds to thesecond target; and c) computing an estimate of a distance between thefirst target and the second target based on at least the image depthmap, the first position information and the second position information;wherein computing the estimate of a distance between the first targetand the second target further includes: c-1) estimating a first targetdistance between the first target and the lens based on the firstposition information, the image depth map, a focus length of the lensfor capturing the image, and a pixel size of the image sensor; and c-2)computing the estimate of the distance between the first target and thesecond target, based on at least the first target distance, the firstposition information, the second position information, and the focuslength of the lens.
 14. The non-transitory computer-readable medium ofclaim 13, the distance estimation system further including a sensormodule for detecting a tilt angle of the image sensor with respect to animaginary vertical line, wherein the software application furtherincludes instructions that, when executed by the processor module,causes the processor module to further: obtain a first pixel positionand a second pixel position on the image sensor based respectively onthe first position information and the second position information, thefirst and second pixel positions corresponding to the first and secondpositions in the image, respectively; calculate a distance between thefirst pixel position and the second pixel position on the image sensor;and compute the estimate of the distance (h₁) between the first targetand the second target using the following equation:$\frac{{h_{11} \cdot {\sin (A)}} + {f \cdot {\sec (A)}}}{d_{1}} = \frac{h_{11} \cdot {\cos (A)}}{h_{1}}$where (h₁₁) represents the distance between the first and second pixelpositions on the image sensor, (A) represents the tilt angle, (f)represents the focus length of the lens, and (d₁) represents the firsttarget distance.
 15. The non-transitory computer-readable medium ofclaim 13, wherein the software application further includes instructionsthat, when executed by the processor module, causes the processor moduleto perform the method, wherein performing the step of computing theestimate of a distance between the first target and the second targetfurther includes estimating a second target distance between the secondtarget and the lens and additionally utilizing the second positioninformation, and computing the estimate of the distance between thefirst target and the second target additionally utilizing the secondtarget distance.
 16. The non-transitory computer-readable medium ofclaim 15, wherein the software application further includes instructionsthat, when executed by the processor module, causes the processor moduleto perform the method to include: obtaining a first pixel position and asecond pixel position on the image sensor based respectively on thefirst position information and the second position information, thefirst and second pixel positions corresponding to the first and secondpositions in the image, respectively; calculating a distance between thefirst pixel position and the second pixel position on the image sensor;and computing the estimate of the distance (h₂) between the first targetand the second target using the following equations:h₂ = d₁² + d₂² − 2 ⋅ d₁ ⋅ d₂ ⋅ cos (K) $K = \frac{h_{33}}{f}$ where(d₁) represents the first target distance, (d₂) represents the secondtarget distance, (h₃₃) represents the distance between the first andsecond pixel positions, and (f) represents the focus length of the lens.17. The non-transitory computer-readable medium of claim 15, thedistance estimation system further including a sensor module fordetecting a tilt angle of the image sensor with respect to an imaginaryvertical line, the image being captured when the tilt angle of the imagesensor is equal to zero degree, wherein the software application furtherincludes instructions that, when executed by the processor module,causes the processor module to perform the method to include: obtaininga first pixel position and a second pixel position on the image sensorbased respectively on the first position information and the secondposition information, the first and second pixel positions correspondingto the first and second positions in the image, respectively;calculating a first distance between the first pixel position and acenter point of the image sensor, and a second distance between thesecond pixel position and the center point of the image sensor; andcomputing the estimate of the actual distance (h₂) between the firsttarget and the second target using the following equations:h₂ = d₁ ⋅ sin (K₁) − d₂ ⋅ sin (K₂)$K_{1} = {\tan^{- 1}\frac{h_{21}}{f}}$$K_{2} = {\tan^{- 1}\frac{h_{22}}{f}}$ where (d₁) represents the firsttarget distance, (d₂) represents the second target distance, (h₂₁)represents the first distance, (h₂₂) represents the second distance, and(f) represents the focus length of the lens.
 18. The non-transitorycomputer-readable medium of claim 13, the distance estimation systemfurther including a display module, wherein the software applicationfurther includes instructions that, when executed by the processormodule, causes the processor module to control the display module todisplay the estimate of the distance on the image.